Spilled paint on a driveway, overspray from a render job, lines left behind by a previous owner, or a painted garage floor you want back to bare concrete. All the same underlying problem and all with the same trap: the methods that remove paint fastest are the ones that damage the slab.
Why pressure alone does not work
Concrete is porous. Wet paint applied to it does not sit on top like it does on a sealed surface — it wicks into the pore structure and cures inside it.
So a pressure washer can remove the paint that is above the surface plane while leaving everything that soaked in. The result is a ghost: a visible stain in roughly the shape of the spill, now surrounded by concrete that has been eroded by the pressure.
That erosion is the real cost. Turning the pressure up far enough to reach paint in the pores means removing the cement paste at the surface, exposing the aggregate, and leaving a patch that is rougher and lighter than everything around it. You have traded a paint stain for a permanent texture difference, which is more noticeable, not less.
It is the same mistake as pressure-washing sandstone: the surface is the thing being removed.
Identify the paint first
The method depends on what it is.
Water-based acrylic — most house paint, most line marking. Softens with the right stripper, comes away reasonably well.
Oil-based enamel — tougher, needs a stronger stripper and more dwell time.
Two-pack epoxy or polyurethane — a garage floor coating or a commercial finish. Chemical strippers are largely ineffective. This is a mechanical job.
Spray paint — if this is graffiti rather than a spill, the surface matters more than the paint, and we have written on that separately in graffiti removal.
Age matters too. Fresh paint, still soft, often comes off with very little drama. Paint that has been there for years has fully cured in the pores and will not.
The methods, in order of aggression
Scraping, for fresh or thick spills. Get the bulk off mechanically before anything else. A sharp floor scraper takes a surprising amount of a thick spill with no risk to the slab.
Chemical stripper. The right answer for most household situations. Modern benzyl alcohol and soy-based strippers are considerably safer than old methylene chloride products and work well, but need longer dwell time — often several hours, sometimes overnight under plastic to stop them drying out.
Apply thick, cover, wait, scrape, repeat. Two gentle applications beat one aggressive one. The commonest failure is impatience: wiping it off before it has fully penetrated.
Caustic soda-based strippers work on acrylics and are harsh on skin and plants. If you use one, neutralise the surface afterwards or the residue interferes with anything you later apply.
Soda blasting. Sodium bicarbonate at pressure. Gentler on the substrate than sand, removes paint well, and the media is water soluble which simplifies cleanup. Good middle option on a decorative or visible slab.
Grinding. A diamond grinder or a surface preparation machine removes paint and a thin layer of concrete with it. Fast, completely effective, and it changes the appearance of the slab — you end up with a ground finish, which on exposed aggregate means losing the aggregate profile.
The right choice for a garage floor being prepared for a new coating, where a ground profile is actually wanted. Usually the wrong choice for a decorative driveway, unless you are prepared to grind the whole thing for consistency.
Shot blasting. Commercial-scale, leaves a heavily profiled surface. Only for slabs that are going to be recoated.
The thing about patch repairs
Whatever method you use, treating one patch of a slab leaves that patch looking different from the rest. Cleaner, lighter, often smoother or rougher.
On a uniform grey driveway this is frequently more conspicuous than the original paint spot. It is worth deciding up front whether you are removing the paint or restoring the driveway, because the second means treating the whole slab.
Sometimes the better answer on a badly marked decorative driveway is to clean the whole surface and accept a faint ghost, rather than chase perfection on one square metre and end up with a patchwork.
Where the stripper goes
Paint residue and chemical stripper must not go into a stormwater drain. In NSW that is a pollution offence, and on a driveway the drain is usually right there.
Contain it, collect the slurry, and dispose of it through a chemical waste facility. Not onto the garden either — stripper will kill plants and it does not break down usefully in soil.
This is set out properly in where the dirty water goes, and it is the part of the job most often got wrong.
If the slab is getting sealed afterwards
Any stripper residue left behind will stop a sealer bonding. Neutralise, rinse thoroughly, and let the slab dry properly — several days, not hours.
Worth planning the sequence in that order rather than discovering it later: paint removal, then any other oil or rust stain treatment, then clean, then dry, then seal.
When to call someone
A small fresh spill is a DIY job. Worth getting help for: large areas, two-pack coatings, decorative or coloured concrete where appearance matters, anything where the runoff has to be contained properly, and any situation where getting it wrong means grinding the whole slab.
See concrete cleaning for how we approach it, including assessing what will realistically come out before committing to a method.
